It's £10 for an adult ticket at my local cinema; £12.20 for 3D (plus £1.50 for the glasses if you don't already have them). And that's just a bog-standard chain cinema - so the normal risk of talking kids, mobile phones, etc.
Food and drink in cinemas is, of course, wildly over-priced, and especially so given the quality (or lack thereof). However, there's an easy fix for that: you don't have to buy it.
We tend to go to the cinema about once a month on average. But we only go to see either 3D films or the big 'spectacle' movies - 3D gives us something we can't replicate at home, while those 'spectacle' films really gain from the cinema's huge screen. For the rest, it's not worth considering - just wait a few weeks and it's out on blu-ray, and can be purchased for less than the price of two cinema tickets.